Performance in working memory and attentional control is associated with the rs2180619 SNP in the CNR1 gene

Translation of animal endocannabinoid models of PTSD mechanisms to humans: Where to next?

The endocannabinoid system is known to be involved in mechanisms relevant to PTSD aetiology and maintenance, though this understanding is mostly based on animal models of the disorder. Here we review how human paradigms can successfully translate animal findings to human subjects, with the view that substantially increased insight into the effect of endocannabinoid signalling on stress responding, emotional and intrusive memories, and fear extinction can be gained using modern paradigms and methods for assessing the state of the endocannabinoid system in PTSD.

Cannabinoid polymorphisms interact with plasma endocannabinoid levels to predict fear extinction learning

BACKGROUND

The endocannabinoid system is gaining increasing attention as a favorable target for improving posttraumatic stress disorder (PTSD) treatments. Exposure therapy is the gold-standard treatment for PTSD, and fear extinction learning is a key concept underlying successful exposure.

METHODS

This study examined the role of genetic endocannabinoid polymorphisms in a fear extinction paradigm with PTSD compared to healthy participants (N = 220). Participants provided saliva for genotyping, completed a fear conditioning and extinction task, with blood samples taken before and after the task (n = 57). Skin conductance was the outcome and was analyzed using mixed models.

RESULTS

Results for cannabinoid receptor type 1 polymorphisms suggested that minor alleles of rs2180619 and rs1049353 were associated with poorer extinction learning in PTSD participants. The minor allele of the fatty acid amide hydrolase (FAAH) polymorphism rs324420 was associated with worse extinction in PTSD participants. Subanalysis of healthy participants (n = 57) showed the FAAH rs324420 genotype effect was dependent on plasma arachidonoyl ethanolamide (AEA) level, but not oleoylethanolamide or 2-arachidonoyl glycerol. Specifically, higher but not lower AEA levels in conjunction with the minor allele of FAAH rs324420 were associated with better extinction learning.

CONCLUSIONS

These findings provide translational evidence that cannabinoid receptor 1 and AEA are involved in extinction learning in humans. FAAH rs324420's effect on fear extinction is moderated by AEA plasma level in healthy controls. These findings imply that FAAH inhibitors may be effective for targeting anxiety in PTSD, but this effect needs to be explored further in clinical populations.

The neural and molecular basis of working memory function in psychosis: a multimodal PET-fMRI study

Working memory (WM) deficits predict clinical and functional outcomes in schizophrenia but are poorly understood and unaddressed by existing treatments. WM encoding and WM retrieval have not been investigated in schizophrenia without the confounds of illness chronicity or the use of antipsychotics and illicit substances. Moreover, it is unclear if WM deficits may be linked to cannabinoid 1 receptor dysfunction in schizophrenia. Sixty-six volunteers (35 controls, 31 drug-free patients with diagnoses of schizophrenia or schizoaffective disorder) completed the Sternberg Item-Recognition paradigm during an fMRI scan. Neural activation during WM encoding and WM retrieval was indexed using the blood-oxygen-level-dependent hemodynamic response. A subset of volunteers (20 controls, 20 drug-free patients) underwent a dynamic PET scan to measure [11C] MePPEP distribution volume (ml/cm3) to index CB1R availability. In a whole-brain analysis, there was a significant main effect of group on task-related BOLD responses in the superior parietal lobule during WM encoding, and the bilateral hippocampus during WM retrieval. Region of interest analyses in volunteers who had PET/fMRI indicated that there was a significant main effect of group on task-related BOLD responses in the right hippocampus, left DLPFC, left ACC during encoding; and in the bilateral hippocampus, striatum, ACC and right DLPFC during retrieval. Striatal CB1R availability was positively associated with mean striatal activation during WM retrieval in male patients (R = 0.5, p = 0.02) but not male controls (R = -0.20, p = 0.53), and this was significantly different between groups, Z = -2.20, p = 0.02. Striatal CB1R may contribute to the pathophysiology of WM deficits in male patients and have implications for drug development in schizophrenia.

Cannabinoid receptor gene polymorphisms and cognitive performance in patients with schizophrenia and controls

Objective:

To test the hypothesis that genetic variations of cannabinoid receptors contribute to the pathophysiology of cognitive deficits in schizophrenia.

Methods:

In this genetic association case-control study, cannabinoid receptor polymorphisms CNR1 rs12720071 and CNR2 rs2229579 were tested for association with neurocognitive performance in 69 patients with schizophrenia and 45 healthy controls. Neurocognition was assessed by the Brief Assessment of Cognition in Schizophrenia (BACS).

Results:

We found a consistent association between CNR1 rs12720071 polymorphism and the cognitive performance of patients in several cognitive domains. Patients with C/C polymorphism presented significantly worse performance in motor speed, verbal fluency, attention/processing speed and reasoning/problem solving.

Conclusion:

Although limited, our data support the hypothesis that CNR1 variations may be associated with the pathogenesis of cognitive deficits of schizophrenia.

Allele-dosage genetic polymorphisms of cannabinoid receptor 1 predict attention, but not working memory performance in humans

Attention and working memory (WM) are under high genetic regulation. Single nucleotide polymorphisms (SNPs) of the CNR1 gene, that encode for CB1R, have previously been shown to be related with individual differences in attentional control and WM. However, it remains unclear whether there is an allele-dosage or a dominant contribution of polymorphisms of CNR1 affecting attention and WM performance. This study evaluated the associations between attention and WM performance and three SNPs of CNR1: rs1406977, rs2180619, and rs1049353, previously associated with both processes. Healthy volunteers (n = 127) were asked to perform the Attention Network Task (ANT) to evaluate their overall attention and alerting, orienting, and executive systems, and the n-back task for evaluating their WM. All subjects were genotyped using qPCR with TaqMan assays; and dominant and additive models were assessed using the risk alleles of each SNP as the predictor variable. Results showed an individual association of the three SNPs with attention performance, but the composite genotype by the three alleles had the greatest contribution. Moreover, the additive-dosage model showed that for each G-allele added to the genotypic configuration, there was an increase in the percentage of correct responses respect to carriers who have no risk alleles in their genotypic configuration. The number of risk alleles in the genotypic configurations did not predict efficiency in any of the attention systems, nor in WM performance. Our model showed a contribution of three single nucleotide polymorphisms of the CNR1 gene to explain 9% of the variance of attention in an additive manner.

Recovery of BDNF and CB1R in the Prefrontal Cortex Underlying Improvement of Working Memory in Prenatal DEHP-Exposed Male Rats after Aerobic Exercise

Early-life exposure to di-(2-ethylhexyl)-phthalate (DEHP) has been suggested to relate to hyperactivity, lack of attention, and working memory deficits in school-age children. Brain-derived neurotrophic factor (BDNF) and endocannabinoids are induced by aerobic exercises to provide beneficial effects on brain functions. This study investigated the mechanisms underlying working memory impairment and the protective role of exercise in prenatal DEHP-exposed male rats. Sprague Dawley dams were fed with vehicle or DEHP during gestation. The male offspring were trained to exercise on a treadmill for 5 weeks, which was followed by an assessment of their working memory with a T-maze delayed non-match-to-sample task. The expressions of BDNF, dopamine D1 receptor (D1R), cannabinoid receptor 1 (CB1R), and fatty acid amide hydrolase (FAAH) in the prefrontal cortex were detected by Western blot. The results showed that DEHP-exposed rats exhibited working memory impairments without significant alterations in locomotor activities. The reduced expressions of prefrontal BDNF and CB1R were obtained in the DEHP-exposed rats, while D1R and FAAH were barely affected. Importantly, aerobic exercise during childhood-adolescence prevented the impairment of working memory in the DEHP-exposed rats by recovering the BDNF and CB1R expressions in the prefrontal cortex. These findings suggest that exercise may provide beneficial effects in ameliorating the impairment of working memory in the prenatal DEHP-exposed male rats at late adolescence.

Endocannabinoids as Therapeutic Targets

Most of the drugs of abuse affect the brain by interacting with naturally expressed molecular receptors. Marihuana affects a series of receptors including cannabinoid receptor 1 (CB1R) and CB2R, among others. Endogenous molecules with cannabinoid activity interact with these receptors naturally. Receptors, ligands, synthesizing and degrading enzymes, as well as transporters, have been described. This endocannabinoid system modulates behaviors and physiological processes, i.e. food intake, the sleep-waking cycle, learning and memory, motivation, and pain perception, among others. The rather broad distribution of endocannabinoids in the brain explains the different effects marihuana induces in its users. However, this very same anatomical and physiological distribution makes this system a useful target for therapeutic endeavors. In this review, we briefly discuss the potential of small molecules that target the endocannabinoids as therapeutic tools to improve behaviors and treat illnesses. We believe that under medical supervision, endocannabinoid targets offer new advantages for patients for controlling multiple medical disorders.

NURR1 and ERR1 Modulate the Expression of Genes of a DRD2 Coexpression Network Enriched for Schizophrenia Risk

Multiple schizophrenia (SCZ) risk loci may be involved in gene co-regulation mechanisms, and analysis of coexpressed gene networks may help to clarify SCZ molecular basis. We have previously identified a dopamine D2 receptor (DRD2) coexpression module enriched for SCZ risk genes and associated with cognitive and neuroimaging phenotypes of SCZ, as well as with response to treatment with antipsychotics. Here we aimed to identify regulatory factors modulating this coexpression module and their relevance to SCZ. We performed motif enrichment analysis to identify transcription factor (TF) binding sites in human promoters of genes coexpressed with DRD2. Then, we measured transcript levels of a group of these genes in primary mouse cortical neurons in basal conditions and upon overexpression and knockdown of predicted TFs. Finally, we analyzed expression levels of these TFs in dorsolateral prefrontal cortex (DLPFC) of SCZ patients. Our in silico analysis revealed enrichment for NURR1 and ERR1 binding sites. In neuronal cultures, the expression of genes either relevant to SCZ risk (Drd2, Gatad2a, Slc28a1, Cnr1) or indexing coexpression in our module (Btg4, Chit1, Osr1, Gpld1) was significantly modified by gain and loss of Nurr1 and Err1. Postmortem DLPFC expression data analysis showed decreased expression levels of NURR1 and ERR1 in patients with SCZ. For NURR1 such decreased expression is associated with treatment with antipsychotics. Our results show that NURR1 and ERR1 modulate the transcription of DRD2 coexpression partners and support the hypothesis that NURR1 is involved in the response to SCZ treatment.SIGNIFICANCE STATEMENT In the present study, we provide in silico and experimental evidence for a role of the TFs NURR1 and ERR1 in modulating the expression pattern of genes coexpressed with DRD2 in human DLPFC. Notably, genetic variations in these genes is associated with SCZ risk and behavioral and neuroimaging phenotypes of the disease, as well as with response to treatment. Furthermore, this study presents novel findings on a possible interplay between D2 receptor-mediated dopamine signaling involved in treatment with antipsychotics and the transcriptional regulation mechanisms exerted by NURR1. Our results suggest that coexpression and co-regulation mechanisms may help to explain some of the complex biology of genetic associations with SCZ.

The effects of cannabinoid 1 receptor compounds on memory: a meta-analysis and systematic review across species

RATIONALE

While cannabis-based medicinal products have been shown to be effective for numerous neurological and psychiatric disorders, the evidence base regarding their adverse cognitive effects is poorly understood. The cannabinoid 1 receptor modulates memory performance via intracellular and extracellular mechanisms that alter synaptic transmission and plasticity. While previous literature has consistently shown that chronic cannabis users exhibit marked cognitive impairments, mixed findings have been reported in the context of placebo-controlled experimental trials. It is therefore unclear whether these compounds inherently alter cognitive processes or whether individuals who are genetically predisposed to use cannabis may have underlying cognitive deficits.

OBJECTIVE

We conducted a meta-analysis to investigate the effects of full and partial cannabinoid 1 receptor (CB1R) agonists, antagonists, and negative allosteric modulators on non-spatial and spatial memory.

METHODS

In accordance with the PRISMA guidelines, the EMBASE, MEDLINE, and PsycINFO databases were systematically searched for studies examining the effects of CB1R agonists, antagonists, and negative allosteric modulators on memory performance.

RESULTS

We systematically reviewed 195 studies investigating the effects of cannabinoid compounds on memory. In humans (N = 35 studies, comprising N = 782 subjects), delta-9-tetrahydrocannabinol (THC) (1.5-5 mg/kg) relative to placebo impaired performance on non-spatial memory tests, whereas only high THC doses (67 mg/kg) impaired spatial memory. Similarly, THC (0.2-4 mg/kg) significantly impaired visuospatial memory in monkeys and non-human primates (N = 8 studies, comprising N = 71 subjects). However, acute THC (0.002-10 mg/kg) had no effect on non-spatial (N = 6 studies, comprising 117 subjects; g = 1.72, 95% confidence interval (CI) - 0.18 to 3.63, p = 0.08) or spatial memory (9 studies, comprising 206 subjects; g = 0.75, 95% confidence interval (CI) - 1.09 to 2.58, p = 0.43). However, acute, full CB1R agonists significantly impaired non-spatial memory (N = 23 studies, 519 subjects; g = - 1.39, 95% CI - 2.72 to - 0.06, p = 0.03). By contrast, the chronic administration of CB1R agonists had no effect on non-spatial memory (N = 5 studies, comprising 146 subjects; g = - 0.05, 95% confidence interval (CI) - 1.32 to 1.22, p = 0.94). Moreover, the acute administration of CB1R antagonists had no effect on non-spatial memory in rodents (N = 9 studies, N = 149 subjects; g = 0.40, 95% CI - 0.11 to 0.92, p = 0.12).

CONCLUSIONS

The acute administration of THC, partial CB1R agonist, significantly impaired non-spatial memory in humans, monkeys, and non-human primates but not rodents. However, full CB1R agonists significantly impaired non-spatial memory in a dose-dependent manner but CB1R antagonists had no effect on non-spatial memory in rodents. Moreover, chronic THC administration did not significantly impair spatial or non-spatial memory in rodents, and there is inconclusive evidence on this in humans. Our findings highlight species differences in the effects of cannabinoid compounds on memory.

Regional changes in the type 1 cannabinoid receptor are associated with cognitive dysfunction in Parkinson's disease

PURPOSE

The endocannabinoid system plays a regulatory role in a number of physiological functions, including motor control but also mood, emotion, and cognition. A number of preclinical studies in Parkinson's disease (PD) models demonstrated that modulating the type 1 cannabinoid receptor (CB₁R) may improve motor symptoms and components of cognitive processing. However, the relation between CB₁R, cognitive decline and behavioral symptoms has not been investigated in PD patients so far. The aim of this study was to examine whether CB₁R availability is associated with measures of cognitive and behavioral function in PD patients.

METHODS

Thirty-eight PD patients and ten age- and gender-matched controls underwent a [¹⁸F]MK-9470 PET scan to assess CB₁R availability, as well as volumetric MR imaging. Neuropsychological symptoms were evaluated using an extensive cognitive and behavioral battery covering the five cognitive domains, depression, anxiety, apathy, and psychiatric complications, and were correlated to CB₁R availability using vowel-wise regression analysis (P < 0.05, corrected for familywise error).

RESULTS

PD patients with poorer performance in episodic memory, executive functioning, speed and mental flexibility (range P 0.003-0.03) showed lower CB₁R availability in predominantly the midcingulate cortex and middle to superior frontal gyrus (T_peak-level > 4.0). Also, PD patients with more severe visuospatial dysfunction showed decreased CB₁R availability in the precuneus, midcingulate, supplementary motor cortex, inferior orbitofrontal gyrus and thalamus (T_peak-level = 5.5). These correlations were not related to cortical gray matter atrophy. No relationship was found between CB₁R availability and mood or behavioral symptom scores.

CONCLUSIONS

Decreased CB₁R availability in the prefrontal and midcingulate cortex in PD patients is strongly correlated with disturbances in executive functioning, episodic memory, and visuospatial functioning. Further investigation of regional CB1R expression in groups of PD patients with mild cognitive impairment or dementia is warranted in order to further investigate the role of CB1R expression in different levels of cognitive impairment in PD.

Gene variants and educational attainment in cannabis use: mediating role of DNA methylation

Genetic and sociodemographic risk factors potentially associated with cannabis use (CU) were investigated in 40 cannabis users and 96 control subjects. DNA methylation analyses were also performed to explore the possibility of epigenetic changes related to CU. We conducted a candidate gene association study that included variants involved in the dopaminergic (ANKK1, NCAM1 genes) and endocannabinoid (CNR1, CNR2 gene) pathways. Sociodemographic data included gender, marital status, level of education, and body mass index. We used MeDIP-qPCR to test whether variations in DNA methylation might be associated with CU. We found a significant association between SNP rs1049353 of CNR1 gene (p = 0.01) and CU. Differences were also observed related to rs2501431 of CNR2 gene (p = 0.058). A higher education level appears to decrease the risk of CU. Interestingly, females were less likely to use cannabis than males. There was a significantly higher level of DNA methylation in cannabis users compared to controls in two of the genes tested: hypermethylation at exon 8 of DRD2 gene (p = 0.034) and at the CpG-rich region in the NCAM1 gene (p = 0.0004). Both genetic variants and educational attainment were also related to CU. The higher rate of DNA methylation, evidenced among cannabis users, may be either a marker of CU or a consequence of long-term exposure to cannabis. The identified genetic variants and the differentially methylated regions may represent biomarkers and/or potential targets for designs of pharmacological therapeutic agents. Our observations also suggest that educational programs may be useful strategies for CU prevention.

A variant on promoter of the cannabinoid receptor 1 gene (CNR1) moderates the effect of valence on working memory

Cannabinoid receptor 1 gene (CNR1) variants have been related to affective information processing and, in particular, to stress release. Here, we aimed to examine whether the endocannabinoid system via CNR1 signaling modulates affective working memory, the memory system that transiently maintains and manipulates emotionally charged material. We focused on rs2180619 (A > G) polymorphism and examined genotype data collected from 231 healthy females. Analyses showed how a general positivity bias in working memory (i.e., better memory for positive words) emerged as task strings lengthened only in carriers of the major allele (AA/AG). Differently, GG carriers showed better memory for affective items in general (i.e., positive and negative words). These findings are some of the first to directly highlight the role of variant on promoter of the CNR1 gene in affective working memory and to evidence a differentiation among CNR1 genotypes in terms of larger difficulties in disengaging from negative stimuli in GG carriers.

Does Cannabis Composition Matter? Differential Effects of Delta-9-tetrahydrocannabinol and Cannabidiol on Human Cognition

Purpose of Review

The lack of clarity about the effect of cannabis use on cognition may be attributable to the considerable heterogeneity among studies in terms of cannabis composition. This article selectively reviews studies examining the distinctive effects of cannabinoids on human cognition, particularly those of delta-9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD).

Recent Findings

Research indicates that ∆9-THC administration acutely impairs cognition, particularly memory and emotional processing. Limited evidence suggests that CBD administration might improve cognition in cannabis users but not in individuals with neuropsychiatric disorders. Moreover, studies indicate that some acute Δ9-THC-induced cognitive impairments may be prevented if Δ9-THC is administered in combination or following CBD treatment. Δ9-THC and CBD have also shown opposite effects on cognition-related brain activation, possibly reflecting their antagonistic behavioral effects.

Summary

Research suggests greater cognitive impairments in individuals when exposed to high ∆9-THC or low CBD cannabis. It is unclear whether at specific concentrations CBD might outweigh any harmful effects of Δ9-THC on cognition.

Prefrontal activity during working memory is modulated by the interaction of variation in CB1 and COX2 coding genes and correlates with frequency of cannabis use

The CB1 cannabinoid receptor is targeted in the brain by endocannabinoids under physiological conditions as well as by delta9-tetrahydrocannabinol under cannabis use. Furthermore, its signaling appears to affect brain cognitive processing. Recent findings highlight a crucial role of cyclooxygenase-2 (COX-2) in the mechanism of intraneuronal CB1 signaling transduction, while others indicate that two single nucleotide polymorphisms (SNPs) (rs1406977 and rs20417) modulate expression of CB1 (CNR1) and COX-2 (PTGS2) coding genes, respectively. Here, our aim was to use fMRI to investigate in healthy humans whether these SNPs interact in modulating prefrontal activity during working memory processing and if this modulation is linked with cannabis use. We recruited 242 healthy subjects genotyped for CNR1 rs1406977 and PTGS2 rs20417 that performed the N-back working memory task during fMRI and were interviewed using the Cannabis Experience Questionnaire (CEQ). We found that the interaction between CNR1 rs1406977 and PTGS2 rs20417 is associated with dorsolateral prefrontal cortex (DLPFC) activity such that specific genotype configurations (CNR1 C carriers/PTGS2 C carriers and CNR1 TT/PTGS2 GG) predict lower cortical response versus others in spite of similar behavioral accuracy. Furthermore, DLPFC activity in the cluster associated with the CNR1 by PTGS2 interaction was negatively correlated with behavioral efficiency and positively correlated with frequency of cannabis use in cannabis users. These results suggest that a genetically modulated balancing of signaling within the CB1-COX-2 pathway may reflect on more or less efficient patterns of prefrontal activity during working memory. Frequency of cannabis use may be a factor for further modulation of CNR1/PTGS2-mediated cortical processing associated with this cognitive process.

Because difficulty is not the same for everyone: the impact of complexity in working memory is associated with cannabinoid 1 receptor genetic variation in young adults

Individual differences in working memory ability are mainly revealed when a demanding challenge is imposed. Here, we have associated cannabinoid 1 (CB1) receptor genetic variation rs2180619 (AA, AG, GG), which is located in a potential CNR1 regulatory sequence, with performance in working memory. Two-hundred and nine Mexican-mestizo healthy young participants (89 women, 120 men, mean age: 23.26 years, SD = 2.85) were challenged to solve a medium (2-back) vs. a high (3-back) difficulty N-back tasks. All subjects responded as expected, performance was better with the medium than the high demand task version, but no differences were found among genotypes while performing each working memory (WM) task. However, the cost of the level of complexity in N-back paradigm was double for GG subjects than for AA subjects. It is noteworthy that an additive-dosage allele relation was found for G allele in terms of cost of level of complexity. These genetic variation results support that the endocannabinoid system, evaluated by rs2180619 polymorphism, is involved in WM ability in humans.

Comparative density of CCK- and PV-GABA cells within the cortex and hippocampus

Cholecystokinin (CCK)- and parvalbumin (PV)-expressing neurons constitute the two major populations of perisomatic GABAergic neurons in the cortex and the hippocampus. As CCK- and PV-GABA neurons differ in an array of morphological, biochemical and electrophysiological features, it has been proposed that they form distinct inhibitory ensembles which differentially contribute to network oscillations and behavior. However, the relationship and balance between CCK- and PV-GABA neurons in the inhibitory networks of the brain is currently unclear as the distribution of these cells has never been compared on a large scale. Here, we systemically investigated the distribution of CCK- and PV-GABA cells across a wide number of discrete forebrain regions using an intersectional genetic approach. Our analysis revealed several novel trends in the distribution of these cells. While PV-GABA cells were more abundant overall, CCK-GABA cells outnumbered PV-GABA cells in several subregions of the hippocampus, medial prefrontal cortex and ventrolateral temporal cortex. Interestingly, CCK-GABA cells were relatively more abundant in secondary/association areas of the cortex (V2, S2, M2, and AudD/AudV) than they were in corresponding primary areas (V1, S1, M1, and Aud1). The reverse trend was observed for PV-GABA cells. Our findings suggest that the balance between CCK- and PV-GABA cells in a given cortical region is related to the type of processing that area performs; inhibitory networks in the secondary cortex tend to favor the inclusion of CCK-GABA cells more than networks in the primary cortex. The intersectional genetic labeling approach employed in the current study expands upon the ability to study molecularly defined subsets of GABAergic neurons. This technique can be applied to the investigation of neuropathologies which involve disruptions to the GABAergic system, including schizophrenia, stress, maternal immune activation and autism.

Functional genetic variation of the cannabinoid receptor 1 and cannabis use interact on prefrontal connectivity and related working memory behavior

Cannabinoid signaling is involved in different brain functions and it is mediated by the cannabinoid receptor 1 (CNR1), which is encoded by the CNR1 gene. Previous evidence suggests an association between cognition and cannabis use. The logical interaction between genetically determined cannabinoid signaling and cannabis use has not been determined. Therefore, we investigated whether CNR1 variation predicts CNR1 prefrontal mRNA expression in postmortem prefrontal human tissue. Then, we studied whether functional variation in CNR1 and cannabis exposure interact in modulating prefrontal function and related behavior during working memory processing. Thus, 208 healthy subjects (113 males) were genotyped for the relevant functional SNP and were evaluated for cannabis use by the Cannabis Experience Questionnaire. All individuals performed the 2-back working memory task during functional magnetic resonance imaging. CNR1 rs1406977 was associated with prefrontal mRNA and individuals carrying a G allele had reduced CNR1 prefrontal mRNA levels compared with AA subjects. Moreover, functional connectivity MRI demonstrated that G carriers who were also cannabis users had greater functional connectivity in the left ventrolateral prefrontal cortex and reduced working memory behavioral accuracy during the 2-back task compared with the other groups. Overall, our results indicate that the deleterious effects of cannabis use are more evident on a specific genetic background related to its receptor expression.